Adding support for regression tests that use a Makefile to build.
This mechanism is needed to support tests that compile the Diderot
program to a library. We have also changed the configuration
process; specify the root of the diderot source to be tested
instead of the path to diderotc.

removing this as something that can be configured, because the utility of the script depends on Teem being built with PNG support, but we do not do that because the diderot compiler does not link with libpng when creating stand-alone executables